The present invention relates generally to synchronization of clocks and, more particularly, to delay measurements and/or synchronization of clocks in a packet-switched communication network.
It may be advantageous in a networked system for devices in the network to have a common time base. The common time base may be used, for example, to trigger coordinated measurement instances in a network of sensors or to coordinate actions of controllers in an industrial system. In addition to sensors and controllers, the system may include computers and communication devices, such as routers.
The electronics industry has developed several standard protocols for use in synchronizing clocks, for example, the Network Time Protocol (NTP) and the Precision Time Protocol (PTP) of IEEE 1588. PTP includes sending timing-related messages between nodes in a communication network. The timing-related messages include, for example, a node transmitting a time-stamped packet to supply its timebase to another node and a node transmitting a packet requesting the receiving node to reply with the time of receipt. Any errors in handling the timing-related messages may be detrimental to accurate clock synchronization and the harm may be cumulative over multiple network devices. Furthermore, efficient handling of timing-related messages is beneficial so as to avoid interfering with other communication.